A related art developing device includes a rotatable developing roller which carries toner, a side seal member which comes into slidable contact with both ends of the developing roller, and a lower film (elongated seal member) which extends in the axial direction of the developing roller and comes into slidable contact with the developing roller (see Patent Document 1). Specifically, according to this technique, a support portion is formed between left and right side seal attachment surfaces, to which the side seal member is attached, to protrude from the side seal attachment surfaces, and a lower film is attached to the support portion.
The lower film is arranged such that both ends thereof overlap the side seal member and are opposite the side seal attachment surfaces. With this structure, in order to further suppress toner leakage, a filler is filled in a gap surrounded by the lower film, the side seal member, the support portion, and the side seal attachment surfaces.
Another related art developing device includes a developing roller (developer carrier) which carries toner, a developing unit housing which rotatably supports the developing roller, and a layer thickness regulating blade, the front end of which comes into slide contact with the developing roller so as to regulate the thickness of toner on the developing roller. Such a developing device has the structure in which the layer thickness regulating blade is separable from the developing unit housing so as to be easily reused (Patent Document 2).
With this structure, two seal members are provided to suppress toner leakage from both ends of the developing roller. One of the two seal members is disposed on the developing unit housing serving as a side seal member adjacent to the leading end of the layer thickness regulating blade, and the other seal member is disposed on the layer thickness regulating blade serving as a blade seal member adjacent to the side seal member. Specifically, part of the blade seal member extends onto the side seal member and is attached to the side seal member. Accordingly, toner leakage from both ends of the developing roller is suppressed, and for reuse, part of the blade seal member is peeled off from the side seal member such that the layer thickness regulating blade can be easily separated from the developing unit housing.
According to the technique described in Patent Document 1, the side seal surface having a width larger than the side seal member is formed in the developing unit housing, and the side seal member attached to the side seal attachment surface is crushed by the developing roller so as to seal between both ends of the developing roller and the developing unit housing. The side seal member is formed by laminating a surface member coming into slide contact with the developing roller and an elastically deformable base material softer than the surface member. The surface member and the base material have the same shape in plan view.
Yet another related art developing device includes a developing roller (developer carrier) which carries toner (developer), a developing unit housing which rotatably supports the developing roller, a layer thickness regulating blade which comes into slide contact with the developing roller so as to regulate the thickness of toner on the developing roller, and a blade rear seal member which is provided between the layer thickness regulating blade and the developing unit housing (Patent Document 3). Specifically, in this developing device, the blade rear seal member is formed shorter than the length of the layer thickness regulating blade in the longitudinal direction, and is disposed inward from both ends of the layer thickness regulating blade in the longitudinal direction. The layer thickness regulating blade is formed by combining a plurality of parts, and a step is formed in a portion which comes into contact with the blade rear seal member.
Yet another related art developing device includes a rotatable developing roller which carries toner, a developing unit housing which has a supply port for supplying toner to the developing roller, and a side seal member which is provided between both ends of the developing roller and the developing unit housing (a portion adjacent to the supply port) so as to come into slidable contact with the developing roller. The side seal member of such a developing device includes an upstream-side base material, a downstream-side base material which is provided on the downstream side of the upstream-side base material (on the downstream side in the rotation direction of the developing roller), and a felt member which is adhered to the upper surfaces of the upstream- and downstream-side base materials so as to come into slide contact with the developing roller (see Patent Document 4).
A developing device, such as a developing cartridge for use in an image forming apparatus, includes a boxlike case with a rectangular opening, a developing roller which is exposed from the opening to supply toner to a photosensitive drum, a layer thickness regulating blade which regulates the thickness of toner on the developing roller, and a seal member which seals a gap between the developing roller or layer thickness regulating blade and the case (for example, see Patent Document 5).
The case of such a developing cartridge has a pair of side walls and upper and lower opening edges forming the opening, and is divided into a boxlike lower frame with an opening on the upper side and a plate-shaped upper frame which is combined so as to cover the opening on the upper side of the lower frame. With this structure, the upper opening edge (beam-like portion) is formed in the lower frame, so the extraction from the mold during manufacturing should be conducted forward from the opening on the front side of the lower frame and upward from the opening on the upper side of the lower frame.    [Patent Document 1] JP-A-2001-27846    [Patent Document 2] JP-A-2007-93951    [Patent Document 3] JP-A-2006-39428    [Patent Document 4] JP-A-2001-22179    [Patent Document 5] JP-A-2006-98770